1. Field of the Invention
The present invention relates to a ratchet tool, and more particularly to a ratchet tool having an improved driving shank for facilitating the driving operation of the ratchet tool.
2. Description of the Prior Art
Various kinds of typical ratchet tools have been developed and comprise an improved gear or internal gear and a pair of pawls moved radially or laterally toward the gear or the internal gear to control the operation directions of the ratchet tools.
For example, U.S. Pat. No. 5,570,616 to Thompson et al., U.S. Pat. No. 5,687,820 to Lin, and U.S. Pat. No. 6,047,802 to Huang disclose three of the typical ratchet screw drivers each including a similar ratchet mechanism to control the operation directions of the ratchet screw drivers.
However, the engagement between the radially or laterally moved pawls and the gear or the internal gear is weak, and thus may not sustain a great rotational driving torque. In addition, the driving stems or the driving tool members of the typical ratchet driving tools may not be changed or replaced with the other ones.
U.S. Pat. No. 5,964,132 to Chen discloses another typical driving tool having a number of shafts to be changeably attached to the driving members. However, no ratchet mechanisms may be disposed in the driving members, and a complicated retaining device is required to changeably attaché the shafts to the driving members.
U.S. Pat. No. 6,058,812 to Casel et al. discloses another typical driving tool having an improved handle, but having a complicated ratchet driving mechanism.
The present applicant has developed another typical driving tool, and disclosed in U.S. Pat. No. 6,622,597 to Chen, and including an improved ratchet driving mechanism. However, the driving shanks or the driving stems may not be rotated relative to the handle, such that the driving tool may not be suitably used for driving some of the fasteners.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional ratchet tools.